Aminopropyl Groups Research Articles

Homocysteine, Infections, Polyamines, Oxidative Metabolism, and the Pathogenesis of Dementia and Atherosclerosis.

Hyperhomocysteinemia is a risk factor for development of dementia and Alzheimer's disease (AD), and low blood levels of folate and cobalamin are associated with hyperhomocysteinemia and AD. In elderly subjects with cognitive decline, supplementation with folate, cobalamin, and pyridoxal demonstrated reduction of cerebral atrophy in gray matter regions vulnerable to the AD process. Multiple pathogenic microbes are implicated as pathogenic factors in AD and atherosclerosis, and the deposition of amyloid-β (Aβ), phosphorylation of tau protein, neuronal injury, and apoptosis in AD are secondary to microbial infection. Glucose utilization and blood flow are reduced in AD, and these changes are accompanied by downregulation of glucose transport, Na, K-ATPase, oxidative phosphorylation, and energy consumption. Thioretinaco ozonide, the complex formed from thioretinamide, cobalamin, ozone, and oxygen is proposed to constitute the active site of oxidative phosphorylation, catalyzing synthesis of adenosine triphosphate (ATP) from nicotinamide adenine dinucleotide (NAD+) and phosphate. Pathogenic microbes cause synthesis of polyamines in host cells by increasing the transfer of aminopropyl groups from adenosyl methionine to putrescine, resulting in depletion of intracellular adenosyl methionine concentrations in host cells. Depletion of adenosyl methionine causes dysregulation of methionine metabolism, hyperhomocysteinemia, reduced biosynthesis of thioretinamide and thioretinaco ozonide, decreased oxidative phosphorylation, decreased production of nitric oxide and peroxynitrite, and impaired host response to infectious microbes, contributing to the pathogenesis of dementia and atherosclerosis.

Hybrid Thin Film Organosilica Sol-Gel Coatings To Support Neuronal Growth and Limit Astrocyte Growth.

Thin films of silica prepared by a sol-gel process are becoming a feasible coating option for surface modification of implantable neural sensors without imposing adverse effects on the devices' electrical properties. In order to advance the application of such silica-based coatings in the context of neural interfacing, the characteristics of silica sol-gel are further tailored to gain active control of interactions between cells and the coating materials. By incorporating various readily available organotrialkoxysilanes carrying distinct organic functional groups during the sol-gel process, a library of hybrid organosilica coatings is developed and investigated. In vitro neural cultures using PC12 cells and primary cortical neurons both reveal that, among these different types of hybrid organosilica, the introduction of aminopropyl groups drastically transforms the silica into robust neural permissive substrate, supporting neuron adhesion and neurite outgrowth. Moreover, when this organosilica is cultured with astrocytes, a key type of glial cells responsible for glial scar response toward neural implants, such cell growth promoting effect is not observed. These findings highlight the potential of organo-group-bearing silica sol-gel to function as advanced coating materials to selectively modulate cell response and promote neural integration with implantable sensing devices.

A spectroscopic study on stability of curcumin as a function of pH in silica nanoformulations, liposome and serum protein

The effect of pH on the stability of curcumin formulated with different carriers has been studied spectroscopically. This was investigated by monitoring the absorption and emission kinetics and fluorescence decay time of four different curcumin formulations suspended in buffer with pH varying from 5 to 8.5. The carriers were organically modified silica NP (SiNP) having 3-amino propyl and/or vinyl groups, liposome and serum protein. The results reveal that stability of curcumin formulated with SiNP functionalized with 3-amino propyl group (SiNP-VA) is significantly higher as compared to SiNP with only vinyl group (SiNP-V) and buffer but lower as compared to serum protein and liposome. However, fluorescence quantum yield (QY) is highest in SiNP-VA among all the nano formulations at pH 7.4 and below, which is attributed to the excited state interaction of curcumin with the amino groups of SiNP-VA. Results suggest that SiNP-VA could be an effective carrier for curcumin, which may have applications for imaging and drug delivery.

Binding and Inhibition of Spermidine Synthase from Plasmodium falciparum and Implications for In Vitro Inhibitor Testing.

The aminopropyltransferase spermidine synthase (SpdS) is a promising drug target in cancer and in protozoan diseases including malaria. Plasmodium falciparum SpdS (PfSpdS) transfers the aminopropyl group of decarboxylated S-adenosylmethionine (dcAdoMet) to putrescine or to spermidine to form spermidine or spermine, respectively. In an effort to understand why efficient inhibitors of PfSpdS have been elusive, the present study uses enzyme activity assays and isothermal titration calorimetry with verified or predicted inhibitors of PfSpdS to analyze the relationship between binding affinity as assessed by KD and inhibitory activity as assessed by IC50. The results show that some predicted inhibitors bind to the enzyme with high affinity but are poor inhibitors. Binding studies with PfSpdS substrates and products strongly support an ordered sequential mechanism in which the aminopropyl donor (dcAdoMet) site must be occupied before the aminopropyl acceptor (putrescine) site can be occupied. Analysis of the results also shows that the ordered sequential mechanism adequately accounts for the complex relationship between IC50 and KD and may explain the limited success of previous efforts at structure-based inhibitor design for PfSpdS. Based on PfSpdS active-site occupancy, we suggest a classification of ligands that can help to predict the KD−IC50 relations in future design of new inhibitors. The present findings may be relevant for other drug targets that follow an ordered sequential mechanism.

Novel indoline derivatives prevent inflammation and ulceration in dinitro-benzene sulfonic acid-induced colitis in rats.

In search of safer treatments for inflammatory bowel disease in subjects not responding to, or showing adverse effects to TNF-α antagonists, we tested three novel indoline carbamates in the 2,4-dinitrobenzene sulfonic acid (DNBS) model of colitis in rats. The compounds have anti-inflammatory activity in other disease models in mice. AN827 (3-(2-(methoxy carbonyl) ethyl) indolin-4-ylethyl methyl) carbamate (0.1 or 1mg/kg), AN680 (3-(2-(methoxy carbonyl) ethyl) indolin-6-ylethyl methyl) carbamate (1.25 or 2.5mg/kg) and AN917 (3-(3-amino propyl) indolin-4-ylethyl methyl) carbamate (1 or 2mg/kg), 5-aminosalycilic acid (5-ASA) (1 or 100mg/kg) or saline (1ml/kg) were administered rectally 1h after intracolonic administration of DNBS, (35mg/kg in 30% alcohol). Disease severity was assessed four days after DNBS administration by change in body weight, colon weight, area of ulceration, myeloid peroxidase (MPO) activity, colonic TNF-α, IL-6 and IL-1β levels. Histopathological scoring was performed after staining colon sections with hematoxylin and eosin and with antibodies to CD68 and CD11b. AN827 (0.1 and 1mg/kg), AN680 (2.5mg/kg) and AN917 (2.0mg/kg) significantly reduced all macroscopic and microscopic parameters of colitis, colonic pro-inflammatory cytokines, TNF-α, IL-1β and IL-6 and MPO activity by about 80%. The indoline derivatives largely prevented the symptoms of colitis and were 500-50 times more potent and more effective than 5-ASA. It may be worth evaluating them in models of established colitis. Since AN827 is strongly bound by plasma proteins no adverse effects are expected if compound is absorbed into the circulation after rectal administration.

Application of amine-functionalized MCM-41 as pH-sensitive nano container for controlled release of 2-mercaptobenzoxazole corrosion inhibitor

In the present study, a pH-responsive corrosion inhibitor system is designed based on aminopropylated MCM-41 as nanocontainer and 2-mercaptobenzoxazole (MBOH) as anti-corrosion agent. This hybrid material shows long-term inhibition capability in 3.5wt% NaCl solution for Cu and stainless steel. The pH-sensitive composite was prepared via grafting the aminopropyl groups to the surface of mesoporous MCM-41 followed by loading of anti-corrosion agent. The XRD, FT-IR, BET, TGA, TEM, and SEM techniques were used to study the morphological and structural properties of the nanocontainer. The loading and releasing properties of nanocontainer were studied using UV–Visible spectroscopy. The results demonstrate that the minimum release rate of MBOH occurs in neutral condition and that with increase of acidity or basicity of the media, the release rate of the corrosion inhibitor from mesoporous silica increases. The self-healing property of nanocontainer was evaluated by electrochemical impedance spectroscopy (EIS). The results of the approach in this paper can be used in many applications where active corrosion protection of materials is required.

One-Dimensional ZnO/Gold Junction for Simultaneous and Versatile Multisensing Measurements.

The sensing capabilities of zinc oxide nano/micro-structures have been widely investigated and these structures are frequently used in the fabrication of cutting-edge sensors. However, to date, little attention has been paid to the multi-sensing abilities of this material. In this work, we present an efficient multisensor based on a single zinc oxide microwire/gold junction. The device is able to detect in real time three different stimuli, UV-VIS light, temperature and pH variations. This is thanks to three properties of zinc oxide its photoconductive response, pyroelectricity and surface functionalization with amino-propyl groups, respectively. The three stimuli can be detected either simultaneously or in a sequence/random order. A specific mathematical tool was also developed, together with a design of experiments (DoE), to predict the performances of the sensor. Our micro-device allows reliable and versatile real-time measurements of UV-VIS light, temperature and pH variations. Therefore, it shows great potential for use in the field of sensing for living cell cultures.

Effect of Various Spinel Ferrite Nanopigments Modified by Amino Propyl Trimethoxy Silane on the Corrosion Inhibition Properties of the Epoxy Nanocomposites

A series of ferrite spinel nanopigments doped with various elements were synthesized via a surfactant-assisted solvothermal method. Then, they were modified with 3-amino propyl trimethoxy silane (APTMS) and characterized by x-ray diffraction analysis, thermal gravimetric analysis, Fourier transform infrared spectroscopy, and energy dispersive x-ray spectroscopy. The unmodified and APTMS modified spinel nanopigments were incorporated into epoxy coatings and their inhibition properties were studied by electrochemical impedance spectroscopy and salt spray test. Results showed that the APTMS modified ZnFe2O4 nanopigment resulted in greater improvement of the barrier action and inhibitive properties of the epoxy coating than Fe3O4 nanopigment.

Heteropolyacids anchored on amino-functionalized MCM-41 and SBA-15 and its application to the ethanol conversion reaction

A series of heteropolyacids (HPA)–silica composites were prepared from H3PMo12O40 (HPM) and H4PVMo11O40 (HPVM) by chemically anchoring to the amine-functionalized mesoporous MCM-41 and SBA-15. These composites were characterized by FT-IR, XRD, N2 adsorption, SEM, and TEM for their structural integrity and physicochemical properties. The effect of the support on thermal stability was investigated by TG–DTG and DTA. The evolved gases during the thermal analysis of prepared composites were identified by online mass spectrometry coupled with TG technique. It was evidenced that HPAs species were finely dispersed on amine-functionalized molecular sieves via chemical immobilization and the structure of the HPAs is preserved over mesoporous materials. From thermal analysis of HPA–silica composites was observed an important mass loss above 553 K which is due to the decomposition of amino propyl functional group. For this reason prepared composites can be utilized as dispersed catalysts for the reactions performed below 553 K. Catalytic properties of these composites were studied by using ethanol conversion at different temperatures. The HPA supported on molecular sieves exhibited an enhanced oxidation catalytic activity (formation of acetaldehyde) and a lower acid catalytic activity (formation of ethylene and diethyl ether) compared to the parent catalysts. The favorable effect of HPAs deposition on silica supports for oxidehydrogenation pathway to acetaldehyde results from the examination of and reaction rate values. For all reaction temperatures, the reaction rates of acetaldehyde formation are higher for supported samples than unsupported ones.

FUNCTIONAL ORGANOSILICON SUBSTANCES AS STABILIZERS OF POLYMERIC SUSPENSIONS

The review presents schemes for obtaining homologous series of the linear α,ω-carbofunctional oligodimethylsiloxanes with the silicone chain length from 6 to 60 siloxane units containing carboxydecyl, aminopropyl and glycidoxypropyl groups at the chain ends allowing to obtain organosilicon surfactants with reproducible structure and properties. Data on the surfactant colloidchemical properties and kinetic regularities of styrene polymerization in their presence are provided. Systematic research of heterophase styrene polymerization kinetic regularities in the presence of water-insoluble α,ω-carbofunctional oligodimethylsiloxane allowed to formulate the fundamental differences of polymerization kinetic regularities from those observed in the presence of water-soluble surfactants. The mechanism of interfacial adsorption layers formation with water-insoluble α,ω-carbofunctional oligodimethylsiloxanes on the surface of monomer drops and polymer-monomeric particles was considered. This mechanism consists in the forced surfactant replacement by the formed polymer (because of their incompatibility) to the interfacial adsorption layer and in the formation of the surfactant supermolecular structures. The latter in total with the polymer provide its high durability.

Delivery of Gemcitabine Prodrugs Employing Mesoporous Silica Nanoparticles.

In this paper, mesoporous silica nanoparticles (MSNs) were studied as vehicles for the delivery of the antitumoral drug gemcitabine (GEM) and of its 4-(N)-acyl derivatives, (4-(N)-valeroyl-(C5GEM), 4-(N)-lauroyl-(C12GEM) and 4-(N)-stearoyl-gemcitabine (C18GEM)). The loading of the GEM lipophilic prodrugs on MSNs was explored with the aim to obtain both a physical and a chemical protection of GEM from rapid plasmatic metabolization. For this purpose, MSNs as such or with grafted aminopropyl and carboxyethyl groups were prepared and characterized. Then, their different drug loading capacity in relation to the nature of the functional group was evaluated. In our experimental conditions, GEM was not loaded in any MSNs, while C12GEM was the most efficiently encapsulated and employed for further evaluation. The results showed that loading capacity increased with the presence of functional groups on the nanoparticles; similarly, the presence of functional groups on MSNs’ surface influenced the drug release profile. Finally, the cytotoxicity of the different preparations was evaluated and data showed that C12GEM loaded MSNs are less cytotoxic than the free drug with an activity that increased with the incubating time, indicating that all these systems are able to release the drug in a controlled manner. Altogether, the results demonstrate that these MSNs could be an interesting system for the delivery of anticancer drugs.

Water-floatable organosilica particles for TiO2 photocatalysis

A water-floatable TiO2 photocatalyst support was successfully produced from organosilica via sol–gel reactions of organosilanes (octyl- and methyl-silyl trichlorides and 3-aminopropyltrimethoxysilane). 3-Aminopropyltrimethoxysilane in silane coupling agents was shown to have an important role in depositing highly dispersed TiO2 nanocrystals onto organosilica particles. Calcination of the as-made sample at 400°C in an airflow resulted in the loss of octyl- and 3-aminopropyl groups, modifying polymethylsiloxane while maintaining water floatability. Calcination led to an increase in the specific surface area from 88 to 230m2/g and the growth of anatase crystallites. Floatability was not observed when the as-made sample was calcined at 600°C, showing that methyl groups acted as surfactants at the air–water interface. Formic acid in water was catalytically oxidized over the water-floatable sample upon irradiation by a solar simulator. The evolved CO2 became saturated when the surface of the aqueous solution was filled with the floating particles. We demonstrated the importance of the floating photocatalyst with respect to the efficiency of light receipt and facile recovery from liquid media.

Aminopropyl-grafted various silica mesostructures for adsorption of molybdenum ions from Re-containing effluent

Four different silica mesostructures, SBA-15 with mesopore size (8.5 nm), SBA-15 with mesopore size (10.3 nm), mesocellular foam (MCF) with uniform cell size (33.2 nm), and MCF with bimodal mesoporosity, were grafted with aminopropyl groups and used for selective recovery of Mo(VI) from Re(VII)-containing effluent. Adsorption isotherms and mechanism of Mo(VI) adsorption on these materials were studied. The adsorbed complexes of Mo(VI) could be formed by ion exchange process or/and by chelation reaction. This study shows a new approach for fractional recovery and separation of Mo(VI) from Re(VII) by using amino-modified SBA-15-type mesoporous silica.

Efficiency of surface modified Ti coated with copper nanoparticles to control marine bacterial adhesion under laboratory simulated conditions

Titanium (Ti) used as condenser material in nuclear power plants encounter severe biofouling in marine environment which in turn affects the efficiency of the metal. To reduce the biofouling by marine microorganisms, surface modification of the Ti was carried out by anodization process to obtain nanotubes (TiO2-NTs). The electrolyte solution containing 1% of ammonium fluoride resulted in uniform growth of TiO2-NTs. TiO2-NTs were further coated with chemically synthesized copper nanoparticles (NT-CuNP) using 3-amino propyl triethoxy silane as a coupling agent. NT-CuNP was characterized by field-emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy and X-ray diffraction. The stability of the coating was determined by the amount of Cu+ ions released into the surrounding using AAS. The microbial adhesion on the surface of Ti, TiO2-NTs and NT-CuNP coupons were evaluated by sea water exposure studies using total viable count method and also characterized by FE-SEM for any morphological changes. The NT-CuNP coupons show a 60% reduction in microbial adhesion when compared to control Ti coupons.

How Micropatterning and Surface Functionalization Affect the Wetting Behavior of ZnO Nanostructured Surfaces

Smart surfaces with a tunable wetting behavior between superhydrophobic and superhydrophilic states are of great interest for different applications, such as novel self‐cleaning/antifogging layers, or in view of the development of microfluidic devices and chemical/biochemical sensors of new generation. This work shows the tuning of the wetting behavior of hydrothermally grown zinc oxide nanowires (NWs) by combining the dual effect resulting from either surface chemical functionalization of the NWs and their growth on substrates prepatterned with different micro‐sized geometries. The characterization results highlight that vertically aligned ZnO NWs successfully cover all the microfeatures of the patterned substrates and can be successfully functionalized with aminopropyl groups. This chemical functionalization drives the initial transition of as‐prepared, superhydrophilic ZnO NWs toward a superhydrophobic regime. Then, protonation/deprotonation of amine groups, induced by their interaction with acid or basic media, changes the wetting state of ZnO NWs between hydrophilic and hydrophobic regimes. Reversible and successful switching from hydrophobic to hydrophilic states can be achieved under ad hoc conditions, in particular using appropriate micropatterns that do not favor the formation and entrapment of air bubbles.

Trap and release of bisphenol-A, 2-naphthol, and doxepin using a 1-hexadecylamine-copper(II)-amine functionalized indium-tin-oxide electrode

An electrically controlled and renewable hydrophobic surface used to trap and release three test pollutants on an indium-tin-oxide (ITO) electrode is presented. Oxygen plasma was used to maximize the activated hydroxyl groups on the ITO surface, which were reacted with (3-aminopropyl) triethoxysilane (APTES) to create a 3-amino propyl layer. Copper(II) ions were introduced and attached to the terminal amine groups. The amine group from 1-hexadecylamine (HDA), complexed the surface-confined copper(II) ions, which resulted in terminal hexadecyl alkyl groups. The created hydrophobic surface was tested for its ability to adsorb pollutant substances, namely bisphenol-A, 2-naphthol, and doxepin. Desorption was accomplished by reducing copper(II) to copper(0) electrochemically. This led to the weakening of the metal-amine complex and the concomitant detachment of the HDA and trapped species from the ITO surface. Efficient trapping and releasing of bisphenol-A (1ppm) was achieved with around 84% adsorption, 100% desorption (in a time course of less than 30s), and 42-fold enrichment on the concentration. After each adsorption/desorption trial, regeneration of the hydrophobic surface was achieved by reapplication of copper(II) ions and HDA. Five cycles were successfully repeated without any significant deterioration in performance. Similar trap-and-release performance was also attained for 2-naphthol and doxepin.

Grafting of [64Cu]-TPPF20 porphyrin complex on Functionalized nano-porous MCM-41 silica as a potential cancer imaging agent

Mesoporous silica, MCM-41, functionalized with 3-aminopropyltriethoxysilane (APTES) was investigated as a potential drug delivery system, using [64Cu]-5, 10, 15, 20-tetrakis penta fluorophenyl porphyrin complex. [64Cu]-TPPF20 complex was grafted on functionalized MCM-41. The product was characterized by paper chromatography, FTIR spectroscopy, low angle X-ray diffraction, CHN and TGA/DTA analyses and atomic force microscopy. The biological evaluations of the grafted complex, [64Cu]-TPPF20@NH2-MCM-41, were done in Fibrosarcoma tumor-bearing Sprague-Dawley rats using scarification studies and Sopha DST-XL Dual-Head SPECT system. The actual loading amount of aminopropyl groups was found about 1.6mmol per gram of final silica. The specific activity of the final compound was found to be 3Ci/g. Amine functionalized MCM-41 was found to be a good platform for theranostic radiopharmaceuticals such as copper-64 complexes. Considering the accumulation of the tracer in tumor cells, fast wash-out from normal tissues, the short half-life copper-64 and less imposed radiation doses to patients, [64Cu]-TPPF20@NH2-MCM-41 can potentially be a suitable candidate for tumor imaging applications and future PET studies.

The Effect of Silane on the Microstructure, Corrosion, and Abrasion Resistances of the Anodic Films on Ti Alloy

Anodic oxide films on Ti-6Al-4V alloy are prepared using sodium hydroxide as the base electrolyte containing aminopropyl trimethoxysilane (APS) as an additive. Some APS undergo hydrolysis, adsorption, and chemical reaction with the TiOx to form Ti-O-Si bond as confirmed by ATR-FTIR and XPS spectra, and in turn their surface appearance and roughness are greatly changed with the addition of APS as observed by their SEM images. These amino anodic films possess much higher corrosive resistances since the formation of Ti-O-Si complex enhances the compactness of the anodic films and the existence of aminopropyl groups inside the pores provides additional blocking effects. Besides, their improvement in anti-abrasive capability is attributed to the toughening effect of the chemically bonded silanes and the lubrication functions from both the chemically bonded and physically absorbed silanes between the touched interfaces.

Enhanced release of baicalin from ordered one-pot-synthesised amine-functionalised mesoporous SBA-15 silica

Baicalin delivery has been controlled using SBA-15 materials functionalised with 3-aminopropyl groups through one-pot synthesis. The quantity of the adsorbed baicalin and the delivery rate can be predetermined using the appropriate structural characteristics and functionality. The release rate of baicalin from SBA-15 functionalised by a one-pot synthesis can be controlled more effectively than that from pure SBA-15, which we primarily ascribe to differences in the drug–matrix interactions.

Interaction of CO2 and CH4 with Functionalized Periodic Mesoporous Phenylene–Silica: Periodic DFT Calculations and Gas Adsorption Measurements

Nonfunctionalized and functionalized periodic mesoporous phenylene–silicas (Ph–PMOs) with different kinds of amine groups were prepared and their capacity to uptake CO2 and CH4 molecules were experimentally evaluated considering biogas upgrading. It was found that aminopropyl groups grafted to the free silanols of the Ph–PMO displayed the highest selectivity for CO2 gas, adsorbing 26.1 times more CO2 than CH4 at 25 °C. The interaction effect of the surface of these materials with the CO2 or CH4 molecules was obtained through the calculation of the Henry constants, and the adsorption mechanisms involved were elucidated from density functional theory calculations. The good synergy between experimental gas adsorption and computational studies suggests that the latter can be used to guide the experimental synthesis of more effective materials. Thus, our computational studies were extended to PMOs with other functional groups having different polarity for predicting interaction energies with CO2 and thus ident...